Exploring The Application Of Perylene Diimide Dimer And Its Derivatives In Organic Solar Cells

Organic solar cells(OSCs),one of the research hotspots,have garnered continuously increasing attention over the past few years owing to their merits of richness in material resources,low cost,solution-processability,light-weight and mechanical-flexibility.Non-fullerene acceptors(NFAs)have been widely used in OSCs due to the inherent advantages of ease synthesis,fine tunability of optical and electrical properties.Perylene diimide(PDI)and its derivatives have been gradually become one of the most promising candidates for NFAs owing to attractive characteristics such as undemanding chemical functionalization,outstanding optoelectronic properties and photothermal stability.In this dissertation,the design,synthesis,and OSCs photovoltaic performance of several novel PDI dimer(PDI2)derivatives-based electron acceptors were systematically investigated.Moreover,the potential application of PDI2 served as solid additive in optimization of device performance was explored.The main research contents and conclusions are given as follows.Firstly,using triphenylamine(TPA)as the core and PDI2 as building blocks,a novel derivative namely TPA-3PDI2,was synthesized.Using the commercially available PTB7-Th as electron donor and TPA-3PDI2 as electron acceptor for OSCs,the photovoltaic performance of room-temperature(RT)spin-coating and hot spin-coating processed photoactive layer were deeply studied.A moderate power conversion efficiency(PCE)of 5.57%was obtained for the RT spin-coating blends based OSCs,while the hot spin-coating blends based devices gave a maximum PCE of 7.04%.The improvements of photovoltaic performance,were rationalized by hot spin-coating processing that could endow the blends with a nanoscale phase morphology,which would reduce the trap-assisted recombination and enhance the exciton dissociation efficiency as well as charge extraction probability.The results illustrated that PDI2 is a desirable building block to construct NFAs,and also,hot spin-coating is a feasible method to achieve considerable PCE in OSCs.Next,an electron acceptor based on tetraphenylethylene(TPE)core flanked with four PDI2 units,coded as TPE-4PDI2,was designed and synthesized.The analogue Tri PE-3PDI2 which consists of triphenylethylene(Tri PE)and three PDI2 panels was synthesized for comparison.Using commercially available PTB7-Th as electron donor,the device performance of TPE-4PDI2 and Tri PE-3PDI2 were investigated.A best PCE of 4.58%was obtained for Tri PE-3PDI2 based OSCs.However,a conspicuous improvement in the photovoltaic performance was achieved for TPE-4PDI2 based OSCs with a much higher PCE of 7.10%.Such an enhancement should be originated from the higher molar extinction coefficient of TPE-4PDI2,as well as better phase morphology and more efficient charge carrier generation,transport and collection process in PTB7-Th:TPE-4PDI2 blend film.These results repeatedly demonstrated that PDI2 is a promising building block for designing high performance NFAs.At last,the effect of PDI2,serving as solid additive,on the photovoltaic performance of the classic OSCs system based on PTB7-Th:PC₇₁BM blends was investigated.As a result,the reference OSCs device without PDI2 exhibited a relatively lower PCE of 7.55%,while the device with 0.8 wt.%addition achieved a much higher PCE of 8.38%,due to the efficient exciton dissociation,weak bimolecular recombination and appropriate phase separation morphology.The results indicated that PDI2 as solid additive shows a great potential in improving the performance of OSCs.In summary,PDI2 is a novel building block,and it also can serve as a solid additive for optimizing the OSCs performance.Moreover,these research results could provide experimental basis as well as theoretical guidelines for further designing high performance PDI based NFAs.